Using a GPU under Linux is not common? And installing Linux on old laptops isn’t either?
As of right now the biggest hurdle is Nvidia without drivers included in Linux. Without a distro that takes care of installing their drivers they are essentially out of luck.
I can’t say anything about AMD, since the last time I had an AMD GPU is ~15 years ago.
When I installed an Ubuntu variant on my G580, which has a Geforce 635M it automatically installed the current driver for Geforce GPUs when I setup the OS, but that driver doesn’t support the 635M. That one needs a legacy driver. And getting that to work was a major pain.
I first installed the legacy driver over apt, but it didn’t do anything, because apparently installing the driver doesn’t actually load the kernel module for the driver. So I had to load it manually, and it still didn’t do anything. Turns out, uninstalling the original driver didn’t unload it from the GPU either. So I had to re-install the old driver, unload the module, uninstall the old driver, install the legacy driver and load the legacy module. Took me a few hours to figure all of that out.
No way someone without CLI experience will be able to do that.